Thermal Dynamics MERLIN 6000, Service Manual, Page: 41 / 112

Manual 0-2569 35 SERVICE TROUBLESHOOTING
NOTE
Measure the voltage while attempting to cut as the
voltage may be correct prior to cutting.
If voltage exceeds 10 vdc, may be momentarily,
perform checks at Section 4.05-P, Steps 2 and
3.
b. Shorted Q1 allows no current control, output
exceeds 175A over current shutdown. Signal
at J3-21 goes low, turning the START signal
OFF. This happens very fast and is difficult to
see. Best way is to check Q1 with an ohmme-
ter. Refer to Section 4.05-M, Switching Con-
trol Check.
c. Faulty Shunt or Switching PCB will prevent
current control, same results as with shorted
Q1, may also cause Q1 to fail. Refer to Section
4.05-N, Switching Control Checks.
d. No Current Sensing Signal (CSR) getting to the
Logic PC Board. Loss of CSR will remove the
START signal. The cause could be a faulty
Switching PC Board current sensing circuit or
a faulty Logic PC Board. Installing a jumper
from TP8 (see Note) to TP1 on the Logic PC
Board should prevent the shutdown.
NOTE
Logic PC Boards with Rev 'D' or later have a test
point, TP8, connected to the anode of D62.
• If shutdown continues, the Logic PC Board is
faulty.
• If transfer is normal and the pilot contactor and
Front Panel PILOT LED goes OFF, then the
Logic PC Board is faulty.
If the PILOT contactor and LED stay ON, check
for a logic low (near zero volts) at J3-11, the CSR
input.
• If low, the Logic PC Board is faulty.
• If not low then the Switching PC Board, Shunt
PC Board, or ribbon cables are faulty.
Main Contactor (W) goes OFF randomly during the cut
1. Contactor goes OFF during the cut from loss of
START signal.
a. Bypass the Standoff Control (SC10) by remov-
ing the ribbon cable between the Standoff Con-
trol (SC10) and the Remote Control (RC6010).
Set the torch to the normal cutting height first
as there will not be power to move the torch
afterwards.
b. If the problem persists, bypass the RC6010 by
removing the CNC cable and connecting a start
switch into the TB2 Start input and operate it
manually. That takes both the remote and con-
troller interface out of the system. If problem
persists go to step 2.
c. If connecting start to TB2 works, move the
switch to the RC 6010 start input at J6-3 and
J6-4 (J6 is the green terminal strip inside the
Remote Control). If still correct , the fault is
with the CNC controller or cables. If problem
has returned the RC6010 or remote cable is
faulty.
2. If connecting START into TB2 did not help, then
the problem is in the power supply. Momentary
or sustained loss of gas pressure or coolant flow
(air bubbles in coolant). If it’s a momentary loss,
it may require an ocilloscope to see the signal.
a. Check for excess bubbling or foaming in the
coolant tank. May be caused by low coolant
level or an air leak on the inlet side of the pump
(radiator, filters). Also, try temporarily jump-
ing out the coolant flow sensor to see if coolant
flow is the cause.
Loss of Start from the Remote Control
The following may prevent or remove the START sig-
nal from the Remote:
1. The CNC STOP MOMENTARY signal input at J29-
5 and J29-6 or J6 -5 and J6-6 is held low.
2. Station select OFF or SW1-B set wrong. Display
will also be OFF.
3. User supplied Enable switch circuit, wires and
switch, have too much resistance. Should not be
more than a couple of ohms. Display will be OFF.
4. Loss of START signal from the CNC. Connect a
normally open switch to the remote start input at
J6- 3 and J6-4 (J6 is green terminal strip inside the
Remote Control) and operate the start manually.
If problem goes away, CNC is at faulty.
5. Standoff Control (SC 10) is faulty. Bypass the SC10
by removing the ribbon cable between the SC10
and RC6010. ). Set the torch to the normal cutting
height first as there will not be power to move the
torch afterwards.
6. Remote Control or interface cable faulty.
O. Pilot Circuit Check
The pilot is ignited by a high voltage spark generated in
the Arc Starter Box. The Arc Starter Box requires a 24
VAC supply which should always be present and a torch